The present invention relates to a discharge lamp lighting apparatus for lighting a discharge lamp at a high frequency using a single-transistor voltage resonance inverter. Moreover, the present invention relates to a luminaire using the discharge lamp lighting apparatus.
A so-called electronic type discharge lamp lighting apparatus wherein a discharge lamp is lighted at a high frequency is now being propagated. Conventionally, a bipolar transistor which is a current drive type switching element has been used for a switching element of a high-frequency inverter which principally constitute the electronic type discharge lamp lighting apparatus. However, a MOSFET which is of a voltage drive type switching element is able to be used recently. Therefore, integrated circuits are widely used as a drive circuit of the switching element. By integrating the drive circuit in a chip, not only the installation of the discharge lamp becomes easy, but also it is able to miniaturize a wiring board and the discharge lamp lighting apparatus.
However, since the high voltage proof MOSFET has a high ON-state resistance, there is a characteristic problem such as a large conduction loss. Therefore, MOSFET is widely used in an inverter like a half-bridge type inverter which can be used at a relatively low voltage.
Accordingly, the bipolar transistor is used for a single-transistor voltage resonance inverter for which a high voltage proof is required. In this case, the switching operation of the bipolar transistor is performed by current feedback using a saturable transformer.
However, the saturable transformer has a drawback of a wide dispersion in characteristics. So, it is difficult to control the quality of the saturable transformer. Moreover, the saturable transformer has another drawback of a wide dispersion in temperature characteristics. Accordingly, a single-transistor voltage resonance inverter had a problem of difficult to design.
When a control circuit suitable for the single-transistor voltage resonance inverter using a bipolar transistor is constituted of an integrated circuit, sufficient base current have to be supplied to the bipolar transistor of the current drive type. Thus, the integrated circuit became upsizing, and the integration was difficult in fact.
The present invention has an object to provide a discharge lamp lighting apparatus principally constituted by a single-transistor voltage resonance inverter using a bipolar transistor, and further, the principal part of its control circuit is constituted by a small integrated circuit. Furthermore, the present invention has another object to provide a luminaire using the discharge lamp lighting apparatus.
In addition, the present invention has another object to provide a discharge lamp lighting apparatus and a luminaire using the lamp system which perform the turn-on operation of the bipolar transistor of the single-transistor voltage resonance inverter effectively.
Furthermore, the present invention has other object to provide a discharge lamp lighting apparatus and a luminaire using the lighting device which start a single-transistor voltage resonance inverter effectively.
To achieve an object of the present invention, a first aspect of the discharge lamp lighting apparatus includes a DC power supply, generating a direct current voltage, an inverter circuit, switching the direct current voltage at a high frequency, and including one bipolar transistor, which is turned on by a feedback signal of the high frequency voltage and turned off by an off-switching signal of a control circuit, and a resonance circuit resonated by the switching operations, a discharge lamp, operated by the high frequency voltage, and the control circuit, provided with a timer, which determines operation-durations including a preheating mode, a starting mode and a lighting mode of the discharge lamp, and an oscillator generating the off-switching signal according to the each mode.
In descriptions of the first aspect and other aspects of the discharge lamp lighting apparatus, some definitions and their technical meanings are presented for following specific terms, unless otherwise specified.
 less than First DC Power Supply greater than 
A first DC power supply is a power source for supplying an electric energy to energizing at least a single-transistor voltage resonance inverter and a discharge lamp. The first DC power supply supplies electrical energy straightforwardly to the single-transistor voltage resonance inverter. The first DC power supply may be any one of a battery power source and a rectified DC power supply. In case of a rectified DC power supply, a voltage of a low-frequency AC power source, for instance, of a commercial AC power source is rectified in order to obtain a DC voltage.
Further, the rectified DC power supply can contain a smoothing circuit as needed. A smoothing circuit may be any of a passive filter containing a partial smoothing circuit wherein a smoothing capacitor is simply coupled across the DC output terminals, a partial smoothing circuit as described below and an active filter such as a chopper. In addition, the partial smoothing circuit is provided with at least a capacitor and a diode, and it outputs a DC output having a rectified waveform of half wave whose valley is filled with a DC voltage up to the middle level. By using an active filter, an input current is enhanced in its power-factor and suppressed in its harmonics. In addition, in order to enhance the power-factor and suppress harmonics of the input current, the single-transistor voltage resonance inverter may be used further to obtain a smoothing DC voltage by using a high-frequency switching operation of the bipolar transistor of the single-transistor voltage resonance inverter.
Furthermore, a first DC power supply can also supply the operating power to the control circuit.
 less than Single-Transistor Voltage Resonance Inverter greater than 
A single-transistor voltage resonance inverter is provided with a single switching element and a resonance circuit where the switching element is coupled to the first DC power supply. The signal-transistor voltage resonance inverter performs the inverter operation for generating a sinusoidal wave AC voltage in the resonance circuit by the switching operation of the switching element turning on and off. Here, the xe2x80x9cone switching transistorxe2x80x9d means that it can be considered a single switching element functionally. Therefore, it may be provided with two or more switching elements coupled in parallel at the point of current capacity.
Further, the first aspect of the discharge lamp lighting apparatus is provided with a bipolar transistor as a switching element of the single-transistor voltage resonance inverter. The turn-on switching operation of the switching element is performed by the feedback control to flow a current to a base of the bipolar transistor. The feedback control is for performing a current feedback of any of a collector current and a resonance current or a lamp current flowing in the resonance circuit, or for performing a voltage feedback of a voltage drop of a current-limiting reactor. Here, the turn-off switching operation of the switching element is performed by using a control circuit. Further, in order to perform the turn-off switching operation easily, it can be provided with a base current cut-off device for short-circuiting between the base and emitter of the bipolar transistor.
Furthermore, a high frequency current can be took out of a secondary winding when the inductor of the resonance circuit is constituted by a primary winding for instance, or a it can lead the voltage drop of the inductor electrically. Here, in the description of the first aspect of the discharge lamp lighting apparatus, the term xe2x80x9chigh frequencyxe2x80x9d means the frequency of around 10 KHz, and more preferably, between 40 KHz to 500 KHz. If the frequency is 10 KHz or more, it realize a lighting device of the discharge lamp which is compact in size and light in weight, and improves the lamp efficiency. Further, if the frequency is from 40 KHz to 500 KHz, it is able to reduce the switching loss and cost of the bipolar transistor.
 less than Discharge Lamp greater than 
It is essential only that a discharge lamp is provided with a pair of filament, so it may have any constitution such as a fluorescent lamp or a bactericidal lamp. The pair of filament electrode is preheated by the high frequency current output from the single-transistor voltage resonance inverter, and the discharge lamp is started and lighted by the high frequency current output from the single-transistor voltage resonance inverter.
In order to light the discharge lamp stably, it is required to connect a current limiting impedance element to the discharge lamp in series. As a current limiting impedance element, it may be any of an inductor, a capacitor, and a resistor. However, an inductor is suitable as a current limiting impedance element.
A single or plural discharge lamps are coupled to the single-transistor voltage resonance inverter. Plural of discharge lamps are coupled in series, in parallel, or in series parallel. Here, in case of coupling the discharge lamps in parallel, the current limiting impedance element is coupled to the discharge lamp in series in each parallel circuit.
In order to heat the filament electrode of the discharge lamp, either one of or both of a filament preheating capacitor circuit and a filament transformer are used. Here, the filament preheating capacitor circuit is a circuit where the capacitor is coupled to the discharge lamp in parallel, and it forms a series resonance circuit with a current-limiting reactor, further it is coupled to at least one of the filament electrodes in series. Moreover, as a filament transformer, a filament heating winding is magnetically coupled to the inductor or the current-limiting reactor of the resonance circuit, or a filament transformer is mounted separately from the single-transistor voltage resonance inverter.
 less than Control Circuit greater than 
A control circuit is a circuit for controlling a turn-off switching operation principally of the single-transition resonance circuit inverter. In the first aspect of the discharge lamp lighting apparatus, the control circuit is constituted principally by an integrated circuit. The control circuit contains a timer and an oscillator. The timer states at power-on to determine at least operation-durations of the preheating mode and the starting mode. The oscillator controls the switching operation of the bipolar transistor of the single-transistor voltage resonance inverter by generating the off-switching signal having cycles suiting the preheating mode, starting mode, and lighting mode at least. Here, the term xe2x80x9cthe operation-duration of the starting modexe2x80x9d means a period for operating the single-transistor voltage resonance inverter in the starting mode. If the discharge lamp is lighted within the period, the lighting of the discharge lamp is detected by a lighting detecting circuit so as to continue the inverter operation. However, when the discharge lamp is not lighted within the period of the starting mode for some reasons, the inverter operation is stopped simultaneously at the end of the starting mode. The inverter operation is stopped by controlling the oscillator for instance.
The timer determines the operation-duration of the oscillator suiting the operation mode. Further, the timer may be constituted to control the cycle, which is the timing of the high level and low level of the off-switching signal generated from the oscillator. Furthermore, the timer may be provided with a time-constant circuit. In this case, the time-constant circuit can be installed external to the integrated circuit in order to easily set up the operation-duration desirably according to the specification.
The oscillator generates an off-switching signal having a cycle suiting the operation mode for a predetermined operation-duration for each operation mode by the timer. In order to generate the off-switching signal, two or more circuits for determining the on-duration or the off-duration of the off-switching signal generated in the oscillator are mounted for each operation mode, and one of them is selected corresponding to the operation mode. Further, in order to fix the on-duration or the off-duration of the off-switching signal, circuits for determining these durations can be constituted by a common single circuit. In this case, for instance, a capacitor charging resistor and two or more capacitor discharging resistors are mounted separately to the capacitor for determining the frequency of the off-switching signal. Thus, the off timing of each period of the off-switching signal is determined by the resistance of the capacitor charging resistor, on the other hand, the on-timing of each period of the off-switching signal is determined by the resistance of the capacitor discharging resistor. Here, two or more capacitor discharging resistors are constituted to have different resistances according to the periods of the off-switching signal required for the operation modes. In the above configuration, according to install the capacitor for determining the timing, the capacitor charging resistor, and a capacitor discharging resistor external to the integrated circuit, the on-duration or the off-duration of the off-switching signal are setup easily desirably according to the specification.
Further, the control circuit can set up other operation modes besides the preheating, starting, and lighting modes. For instance, when a modulated light level control circuit is included in the integrated circuit, the period of the off-switching signal can be controlled to be a period suitable for modulating light by receiving the modulated light signal from outside. Here, the modulated light may be any of continuous modulated light and gradual modulated light.
Furthermore, the integrated circuit of the control circuit includes an input voltage fluctuation compensation circuit. That is, when using a rectified DC power supply, it is practically important to cope with a fluctuation of the commercial AC power source voltage not to affect to the operation of the discharge lamp as much as possible. The input voltage fluctuation compensation circuit is one of the countermeasures, and it is able to avoid or reduce the effect caused by the fluctuation of the commercial AC power source voltage. Here, since the input voltage fluctuation affects little to the operation of the discharge lamp during the preheating mode, the input voltage fluctuation compensation circuit can be suspended. Furthermore, the input voltage fluctuation compensation circuit can operated only during the lighting mode. Accordingly, the circuit configuration of the integrated circuit is simplified.
Moreover, a the integrated circuit of the control circuit includes a high frequency current stabilizing circuit. The high frequency current stabilizing circuit operates to stabilize the high frequency current by feeding back the current flowing in the single-transistor voltage resonance inverter or the discharge lamp during the lighting operation of the discharge lamp.
 less than Operations greater than 
In the first aspect of the discharge lamp lighting apparatus, the timer of the control circuit determines the operation-durations set up beforehand in response to each operation mode of at least preheating, starting, and lighting of the discharge lamp. Thus, it is able to allow optimum periods for every operation modes suiting the discharge lamp characteristics. Accordingly, the life of the discharge lamp is not interfered because of the improper operation-duration.
Further, the oscillator generates an off-switching signal having a cycle that is set up for each operation mode by interlocking with the determination of the operation-duration of each operation mode. Therefore, it is able to supply the high frequency current suitable for each operation mode to the discharge lamp.
Furthermore, since the switching frequency is appropriately controlled by the control circuit, not only the influence on the temperature characteristics etc. becomes small, but also it becomes easy to integrate the inverter in a chip.
Moreover, the single-transistor resonance inverter can be provided with a bipolar transistor which has a high voltage proof property and a characteristic problem free property for a switching element. Since the turn-on switching operation of the bipolar transistor is controlled by using the feedback signal, and the turn-off switching operation of it is controlled by using the off-switching signal generated from the oscillator, the switching operation of the bipolar transistor is controlled effectively even though the principal part of the control circuit is integrated in a chip.
Furthermore, by integrating the principal part of the control circuit in a chip, it easily integrates a protection circuit to the abnormal condition caused at the life terminal, an input voltage fluctuation compensation circuit, or a high frequency current stabilizing circuit, so that it is able to realize various functions control.
Furthermore, by integrating the principal part of the control circuit in a chip, the circuit installation of the discharge lamp becomes easy, it is able to realize a discharge lamp whose circuit board is compact in size and light in weight.
To achieve an object of the present invention, a second aspect of the discharge lamp lighting apparatus includes a DC power supply, generating a direct current voltage, an inverter circuit, switching the direct current voltage at a high frequency, and including one bipolar transistor, which is turned on by a feedback signal of the high frequency voltage and turned off by an off-switching signal of a control circuit, and a resonance circuit resonated by the switching operations, a discharge lamp, operated by the high frequency voltage, a current transformer, feeding back a lamp current of the discharge lamp to turn on the bipolar transistor, a base current cut-off device responsive to the off-switching signal of the control circuit to cut off a base current of the bipolar transistor, and the control circuit, provided with a timer and an oscillator, wherein the timer determines operation-durations including a preheating mode, a starting mode and a lighting mode of the discharge lamp, and supplies a starting current to the bipolar transistor, and the oscillator provides the base current cut-off device with the off-switching signal which varies to regulate an on-duration of the base current cut-off device according to the each mode.
The second aspect of the discharge lamp lighting apparatus is configured to turns on the bipolar transistor that is a switching element of the single-transistor voltage resonance inverter effectively. That is, when the power is turned on, a starting current is applied to the bipolar transistor from the control circuit so as to apply timing for turning on to the bipolar transistor. Then, the current flows to the resonance circuit of the single-transistor voltage resonance inverter, thus, the bipolar transistor is started and the discharge lamp is lighted. When the discharge lamp is lighted, as the result of the current being fed back to the base of the bipolar transistor by the current feedback circuit, the operation of the single-transistor voltage resonance inverter is shifted to the regular operation. Consequently, the lighting of the discharge lamp is performed smoothly. Here, the turn-on operation of each cycle during the regular operation is performed by the current supplied from the current feedback circuit.
In addition, when the primary winding of the current transformer of the current feedback circuit is coupled to the collector of the bipolar transistor of the single-transistor voltage resonance inverter in series, the current does not flow to the current transformer unless the bipolar transistor is turns on. Therefore, there is a drawback that the current feedback circuit does not contribute to the turn-on operation of the bipolar transistor.
By the way, in the single-transistor voltage resonance inverter, there are two factors to turn on the bipolar transistor in each cycle. The one factor is a current supplied from a current feedback circuit. The other factor is a resonance current which flows from the base to the collector during the off-duration of the bipolar transistor. In the latter, when the resonance current flows from the base to the collector, the electron which is a minority carrier will be accumulated in a base region. Then, when the polarity of the resonance current is reversed, and the positive voltage is applied to the collector, the current flows from the collector to the based in order to emit the minority carrier accumulated in the base region. At this time, a part of the current flows also to an emitter. Therefore, also in the configuration in which the primary winding of the current transformer is connected to the collector of the bipolar transistor, the turn-off operation of each cycle is performed effectively by the current flows from the collector to the emitter associating with the emission of the minority carrier accumulated in the base region when the polarity of a resonance current is reversed. However, since there is a possibility that the base collector current does not flow in the situation where the power supply voltage and the lighting condition of the discharge lamp, the turn-on operation of each cycle is performed by the starting current from the control circuit under this condition.
However, the starting current obtained from the control circuit is about several mAs, and is a small value when it is compared with the current obtained from the current feedback circuit. Thus, since the turn-operation performed by a small starting current is influenced by the capacity component between base and emitter greatly, the timing of the turn-on operation is delayed, and it may worsen the switching operation.
Then, in the second aspect of the discharge lamp lighting apparatus, the primary winding of the current transformer in the current feedback circuit is connected in the current path of the discharge lamp. As the result, the bipolar transistor is certainly turned on in each cycle by the current supplied from the current feedback circuit. Here, the term xe2x80x9cthe current path of the discharge lampxe2x80x9d means the passage of a current which influences directly to a load current or a load current which flows to the discharge lamp. Therefore, for instance, when the output transformer is intervened between the bipolar transistor of the single-transistor voltage resonance inverter and a discharge lamp, the primary winding of the current transformer may be connected directly in the secondary side circuit of the output transformer, or it may be connected directly in the primary side circuit of the output transformer.
Furthermore, there is the necessity that a phase of the current fed back from the secondary winding of the current transformer to the base circuit of the bipolar transistor is adjusted to a phase of the load current in a predetermined relation. In order to perform this adjustment appropriately, a phase matching circuit can be interposed between the secondary winding of the current transformer and the base circuit of the bipolar transistor. The phase matching circuit may adopt a constitution according to the position for inserting the primary winding of the current transformer as needed.
Then, in the second aspect of the discharge lamp lighting apparatus, the run-on operation of each cycle of the bipolar transistor in the single-transistor voltage resonance inverter is performed by the current supplied to the base form the secondary winding of the current transformer, since the primary winding of the current transformer in the current feedback circuit is connected in the current path of the discharge lamp. Therefore, a turn-on operation of the bipolar transistor is performed with reliability and stability.
Furthermore, the turn-off operation of the bipolar transistor is performed by short-circuiting a base current by the base current cut-off device, when the off-switching signal generated from the control circuit is an on-duration. Although the on-duration of the off-switching signal is fixed, the off-duration varies according to a control pattern as needed. When the off-switching signal is low in level, the base current cut-off device will be in an open state. Therefore, when the current is fed back from the current transformer to the base, the bipolar transistor is turned off.
To achieve an object of the present invention, a third aspect of the discharge lamp lighting apparatus includes a first DC power supply, generating a first direct current voltage, an inverter circuit, switching the first direct current voltage at a high frequency, and including one bipolar transistor, which is turned on by a feedback signal of the high frequency voltage and turned off by an off-switching signal of a control circuit, and a resonance circuit resonated by the switching operations, a discharge lamp, operated by the high frequency voltage, a base current cut-off device responsive to the off-switching signal of the control circuit to cut off a base current of the bipolar transistor, a starting current controller, controlling a second direct current voltage supplied from a second DC power supply provided in the control circuit to the base of the bipolar transistor for a predetermined period in a starting operation, and the control circuit, provided with an oscillator defining the high frequency for operating the inverter and regulating the frequency of the off-switching signal.
The third aspect of the discharge lamp lighting apparatus is so configured that the starting current flows only when necessary.
The starting current for starting the bipolar transistor that is a switching element of the inverter is supplied to the base of the bipolar transistor via a current limiting resistor from a rectified DC power supply or a reference potential source constituted in the control circuit in general. In the inverter providing the current feedback circuit, the current is fed back to the base of the bipolar transistor by the current feedback circuit after it is started. Therefore, the regular operation is performed continuously.
However, in a non-load state where the discharge lamp is not installed in the load circuit, the load circuit is opened. Therefore, even if there is the current feedback circuit, current is not fed back to the base of the bipolar transistor. However, it is possible to turn on the bipolar transistor without depending on the current feedback to its base from a current feedback circuit. That is, as mentioned above, when the resonance current flows to the collector from the base, the electron which is a minority carrier will be accumulated in a base region. Then, when the polarity of the resonance current is reversed, and the positive voltage is applied to the collector, the current flows from the collector to the based in order to emit the minority carrier accumulated in the base region. Thus, the bipolar transistor is turned on.
In the single-transistor voltage resonance inverter of a self-oscillation control system, the frequency will not be appropriately controlled, and the operation frequency will be lowered when it becomes the oscillation state in the non-load state. Therefore, the resonance voltage rises to exceed the pressure proof of the bipolar transistor, thus the bipolar transistor is destroyed. Moreover, in the single-transistor voltage resonance inverter of a fixed frequency control system, the resonance frequency lowers when it becomes the non-load state, and time width of the resonance voltage is expanded. As the result, the bipolar transistor is turned on by the starting current before the collector voltage lowers up to 0 V, thus, the null voltage switching operation will not be performed. Therefore, the switching loss of the bipolar transistor is increased, and there is a case that the bipolar transistor is destroyed. That is, in the single-transistor voltage resonance inverter of either the self-oscillation control system or the fixed frequency control system, there is a case that the bipolar transistor is destroyed when it is in the non-loaded state.
Next, referring now to the attached drawings, FIGS. 12a to 12d and FIGS. 13a and 13b, it will explained that the reasons to increase the switching loss by the oscillation in the non-load state, and thus the switching loss causes to destroy the bipolar transistor.
FIGS. 12a to 12d are waveform diagrams showing the voltage and current waveform of each portion of the single-transistor voltage resonance inverter. FIG. 12a is a waveform diagram showing the waveform of a collector-emitter voltage VCE. FIG. 12b is a waveform diagram showing a current waveform of a collector current IC. FIG. 12c is a waveform diagram showing a current waveform of a base current IB. FIG. 12d is a waveform diagram showing a voltage waveform of a voltage between the base and emitter VBE. FIGS. 13a and 13b are enlarged diagrams of a current waveforms of the voltage waveform of the voltage across and through the collector-emitter VCE shown in FIG. 12a and a current waveform of the collector current IC shown in FIG. 12b. 
Especially, as seen from FIG. 13b, a collector current flows though it is small in the non-load state as shown by an arrow shows. Therefore, the operation of the bipolar transistor becomes class A operation during the period. Thus, the switching loss applied by xe2x80x9ccollector-emitter voltage VCExc3x97collector-current ICxe2x80x9d occurs in a bipolar transistor. Therefore, if the starting current continues flowing in the non-load state, the switching loss will increase and the bipolar transistor is destroyed. In order to solve this problem, it is effective to limit the starting current and to control the loss of the transistor. However, when the starting current is lowered, there will be a problem to lower the starting function which is the essential function of the starting circuit.
Then, the third aspect of the discharge lamp lighting apparatus is configured that the starting current is supplied to the base of the bipolar transistor only within the predetermined time at the time of starting operation. That is, the second DC power supply for supplying the current to the vase circuit of the bipolar transistor of the switching element is mounted on the control circuit of the single-transistor voltage resonance inverter. Furthermore, a starting current controller for controlling to supply the base current only within the predetermined time at the time of the starting operation is interposed between the second DC power supply and the base circuit of the bipolar transistor. As the starting current controller, if it satisfies the conditions mentioned above, the concrete configuration of it will not be asked. For example, a starting current controller is able to be provided with a differentiating circuit or a switch which is timer-controlled. Here, the starting current below necessary quantity may flow continuously. Moreover, the second DC power supply may have a current capacity to the extent of supplying the base current to the bipolar transistor. Therefore, when the principal part of the control circuit is integrated in a chip, the constant voltage power source is mounted in the integrated circuit.
In the third aspect of the discharge lamp lighting apparatus, it can be started by supplying the starting current to the base of the bipolar transistor only within the predetermined time at the starting operation. Therefore, the starting characteristics is not lowered. Furthermore, the destruction of the bipolar transistor caused by increase of the switching loss which originates in the starting current at the time of the oscillation in a no-load state is prevented.
To achieve an object of the present invention, a fourth aspect of the discharge lamp lighting apparatus includes a DC power supply, generating a direct current voltage, an inverter circuit, switching the direct current voltage at a high frequency, and including one bipolar transistor, which is turned on by a feedback signal of the high frequency voltage and turned off by an off-switching signal of a control circuit, and a resonance circuit resonated by the switching operations, a discharge lamp, operated by the high frequency voltage, and the control circuit, provided with a timer regulating operation modes of the discharge lamp, and an oscillator generating the off-switching signal according to each operation mode of the discharge lamp.
The forth aspect of the discharge lamp lighting apparatus is configured to suitably carries out a turn-off switching operation of the bipolar transistor in the single-transistor voltage resonance inverter. That is, a control circuit contains a timer and an oscillator. The timer determines the time for operating the oscillator as needed. Moreover, an oscillator generates an off-switching signal. The turn-off switching operation of the bipolar transistor is controlled by the off-switching signal.
In the fourth aspect of the discharge lamp lighting apparatus, the control circuit contains a timer and an oscillator, and the turn-off switching operation of the bipolar transistor in the single-transistor voltage resonance inverter is controlled by the timer and the oscillator. Therefore, the control of the turn-off switching operation is performed with reliability and a circuit configuration is simplified.
Further to the fourth aspect of the discharge lamp lighting apparatus, in a fifth aspect of the discharge lamp lighting apparatus, the control circuit is provided with a lamp life terminal detecting circuit for detecting the life terminal of the discharge lamp, a lamp installation detecting circuit for detecting the installation of the discharge lamp, a lamp life terminal determining circuit for determining the life terminal in response to the output of the lamp life terminal detecting circuit, a lamp installation determining circuit for determining the lamp installation in response to the output of the lamp installation detecting circuit, and wherein it is characterized by that the control circuit carries out a protective action when a lamp life terminal is determined, and releases the protective action when a lamp installation is determined.
The fifth aspect of the discharge lamp lighting apparatus is configured to accommodate a circuit for carrying out a protective action by detecting a lamp life terminal and a circuit for releasing the protective action when the lamp installation is detected.
 less than Lamp Life Terminal Detecting Circuit greater than 
When the discharge lamp comes to the life terminal, its discharge becomes a half-discharge, and the DC component is superimposed on the lamp current. Therefore, by detecting the DC component, the life terminal of the discharge lamp is easily detected. In addition, the lamp life terminal detecting circuit may be any configuration if it is a circuit for detecting the life terminal of the discharge lamp.
 less than Lamp Installation Detecting Circuit greater than 
When the discharge lamp is installed on correctly, the single-transistor voltage resonance inverter is in a loaded state. Moreover, when the discharge lamp is not installed on correctly, the single-transistor voltage resonance inverter is in a non-loaded state. Therefore, the lamp installation is detected by detecting the extent of the load. Here, the lamp installation detecting circuit may be any configuration only if it is a circuit for detecting the installation of the discharge lamp. In this case, it is able to detect the extent of the lamp installation by determining the extent of the load.
 less than Circuit Integration greater than 
In the integrated circuit, a lamp life terminal determining circuit and a lamp installation determining circuit are integrated further to the principal part of the control circuit explained in the first embodiment. The lamp life terminal determining circuit determines the lamp life terminal according to the output of the lamp life terminal detecting circuit, so as to perform the protective action. The lamp installation determining circuit determines the lamp installation according to the output of the lamp installation detecting circuit. As a protective action, for instance, the operation of the single-transistor voltage resonance inverter is forced to stop. Here, if the lamp determined the life terminal is replaced for a good lamp, the protective action is released in response to the lamp replacement, thus the operation of the discharge lamp lighting apparatus is reset to the original operation automatically.
 less than Operation greater than 
In the fifth aspect of the discharge lamp lighting apparatus, when the discharge lamp comes to the life terminal, the lamp life terminal detecting circuit detects the life terminal of the discharge lamp. If the lamp life terminal is detected, the lamp life terminal determining circuit integrated in the integrated circuit determines the lamp life terminal. Then, the lamp life terminal determining circuit determines that the discharge lamp is in the terminal stage where it needs the protective action, the lamp life terminal determining circuit, for instance, generates a shut-down signal to shut-down the operation of the single-transistor voltage resonance inverter compulsorily in order to perform the protective action. When the lamp installation detecting circuit detects the replacement of the lamp in the life terminal for a good lamp, the protective action is released by the lamp installation determining circuit in accordance with the detection, thus the inverter operation is reset. Accordingly, since it is provided with a function for releasing the protective action when the active lamp determined the life terminal is replaced to a good lamp, the discharge lamp can be lighted safely again automatically even though the power source is not powered-on again.
Here, even when the discharge lamp is not installed perfectly, the protective action is performed by detecting the insufficient installation. In this case, the insufficient installation of the discharge lamp is detected in the lamp installation detecting circuit. Then, the lamp installation determining circuit generates a shut-down signal to shut-down the operation of the single-transistor voltage resonance inverter operation compulsorily in order to perform the protective action in according to the detection of insufficient installation.
As the result, it is able to ensure safety of the discharge lamp lighting apparatus.
Further to the fourth aspect of the discharge lamp lighting apparatus, a sixth aspect of the discharge lamp lighting apparatus is characterized by that the off-switching signal consists of an on-duration and an off-duration, and that the control circuit controls a frequency of the off-switching signal by regulating the off-duration of the off-switching signal while leaving the on-duration of the off-switching signal constant.
The sixth aspect of the discharge lamp lighting apparatus is configured to easily carry out a turn-off switching operation of the bipolar transistor. That is, a base current cut-off device, for instance a MOSFET having small current capacity is coupled between the base and the emitter of the bipolar transistor. If it is constituted that the base and the emitter is short-circuited when the electric switch is turned on in order to perform the off switching operation of the bipolar transistor, the circuit arrangement of the single-transistor voltage resonance inverter is relatively simplified. According to the sixth aspect of the discharge lamp lighting apparatus, the turn-off switching operation of the bipolar transistor is able to be performed certainly by only applying the off-switching signal to the single-transistor voltage resonance inverter having such a circuit arrangement. Further, while the off-switching signal is kept in the on-duration, the bipolar transistor is kept being turned of.
After the off-switching signal is not in the high-level state, and the base current cut-off device is turned off, the current flows from the current transformer to the base of the bipolar transistor, so that the bipolar transistor is turned on.
By repeating above mentioned off and on switching operations of the bipolar transistor, the single-transistor voltage resonance inverter performs the inverter operation. As the result, the generated AC output is supplied to the discharge lamp. Further, the off-duration of the off-switching signal varies, the cycle of the off-switching signal varies, and then the oscillation frequency also varies. According to the change of the oscillation frequency, the operation frequency of the single-transistor voltage resonance inverter changes. As the result, the frequency of the resonance circuit decreases, while the high frequency output current increases. Therefore, by selecting the operation frequency according to the operation mode of the discharge lamp, the preheating, the starting, and the lighting of the discharge lamp can be optimized.
As mentioned above, in the sixth aspect of the discharge lamp lighting apparatus, the circuit arrangement is simplified for performing the off switching operation of the bipolar transistor in the single-transistor voltage resonance inverter. Further to the fourth aspect of the discharge lamp lighting apparatus, a seventh aspect of the discharge lamp lighting apparatus is characterized by that the frequency of the off-switching signal is determined by an external device to the control circuit.
The seventh aspect of the discharge lamp lighting apparatus is configured to suitably integrate the control circuit which can be used for various discharge lamps in common in a chip. That is, there are different demands to the cycle of the off-switching signal generated from the oscillator depends on the discharge lamp or the way to control of the discharge lamp in general. In the seventh aspect of the discharge lamp lighting apparatus, a circuit device involved in deciding a cycle of the off-switching signal is constituted to be integrated externally. Therefore, the integrated circuit is able to be shared to the equipment of different specification only by changing the external device for a required one, or only by changing the capacitance or the resistance of the external device.
To achieve an object of the present invention, a eighth aspect of the discharge lamp lighting apparatus includes a DC power supply, generating a direct current voltage, an inverter circuit, switching the direct current voltage at a high frequency, and including one bipolar transistor, which is turned on by a feedback signal of the high frequency voltage and turned off by an off-switching signal of a control circuit, and a resonance circuit resonated by the switching operations, a discharge lamp, operated by the high frequency voltage, a current transformer, having a primary winding of the transformer inserted in a current path of the discharge lamp and a secondary winding inserted in a base current path of the bipolar transistor, thereby feeding back a lamp current of the discharge lamp to the base of the bipolar transistor to turn on the bipolar transistor through the primary winding and the secondary winding, a base current cut-off device responsive to the off-switching signal of the control circuit to cut off a base current of the bipolar transistor, and the control circuit, provided with a timer regulating operation modes of the discharge lamp, and an oscillator providing the base current cut-off device with the off-switching signal which varies in its frequency to regulate an on-duration of the base current cut-off device according to the operation mode of the discharge lamp.
The eighth aspect of the discharge lamp lighting apparatus is configured to favorably carries out the turn-on operation of the bipolar transistor which is a switching element of the single-transistor voltage resonance inverter effectively. The eighth aspect of the discharge lamp lighting apparatus differs from the second aspect of the discharge lamp lighting apparatus by that the requirements for the control circuit are simplified. That is, the timer controls the operation-duration of the oscillator as needed. On the other hand, the fifth embodiment is same as the second embodiment in that the oscillator generates the off-switching signal in response to the control of the timer.
In the eighth aspect of the discharge lamp lighting apparatus, the ON of the base current cut-off device varies according to the control pattern as needed. Therefore, it is able to turn on the bipolar transistor certainly in response to the timing of the applied current via the current transformer.
Further, the base current cut-off device is turned on by the off-switching signal applied from the control circuit, and the base current is short-circuited, so that the bipolar transistor is turned off.
To achieve an object of the present invention, a luminaire includes a body, and a discharge lamp lighting apparatus, as defined in the fourth aspect of the invention, mounted on the body.
In the ninth aspect of the invention, the term xe2x80x9cluminaire xe2x80x9d has a wide concept including any devices for utilizing light radiated from the discharge lamp. That is, the luminaire according to the present invention is such as a lighting unit, an image readout device, a display device, an ultraviolet rays generating device, and a screw-base-mount type fluorescent lamp in specific.
Furthermore, the body means a whole portion of the luminaire except the discharge lamp lighting apparatus. A lighting circuit potion of the discharge lamp lighting apparatus is able to be mounted separately from the body.
Additional objects and advantages of the present invention will be apparent to persons skilled in the art from a study of the following description and the accompanying drawings, which are hereby incorporated in and constitute a part of this specification.